Lewis notation and molecular structure

Although we have used diagrams to show the structure of molecules, there are other forms of notation that can be used, such as
Lewis notation and
Couper notation .
Lewis notation uses dots and crosses to represent the
valence electrons on different atoms. The chemical symbol of the element is used to represent the nucleus and the core electrons of the atom.

So, for example, a hydrogen atom would be represented like this:

A chlorine atom would look like this:

A molecule of hydrogen chloride would be shown like this:

The dot and cross in between the two atoms, represent the pair of electrons that are shared in the covalent bond.

Represent the molecule
H2O using Lewis notation

For each atom, determine the number of valence electrons in the atom, and represent these using dots and crosses.

The electron configuration of hydrogen is 1s
1 and the electron configuration for oxygen is 1s
2 2s
2 2p
4 . Each hydrogen atom has one valence electron, which is unpaired, and the oxygen atom has six valence electrons with two unpaired.

Arrange the electrons so that the outermost energy level of each atom is full.

For each atom, determine the number of valence electrons that the atom has from its electron configuration.

The electron configuration of hydrogen is 1s
1 , the electron configuration of nitrogen is 1s
2 2s
2 2p
3 and for carbon is 1s
2 2s
2 2p
2 . This means that hydrogen has one valence electron which is unpaired, carbon has four valence electrons, all of which are unpaired, and nitrogen has five valence electrons, three of which are unpaired.

Arrange the electrons in the HCN molecule so that the outermost energy level in each atom is full.

The HCN molecule is represented below. Notice the three electron pairs between the nitrogen and carbon atom. Because these three covalent bonds are between the same two atoms, this is a
triple bond.

Hydrogen has an electron configuration of 1s
1 and sulfur has an electron configuration of 1s
2 2s
2 2p
6 3s
2 3p
4 . Each hydrogen atom has one valence electron which is unpaired, and sulfur has six valence electrons. Although sulfur has a variable valency, we know that the sulfur will be able to form 2 bonds with the hydrogen atoms. In this case, the valency of sulfur must be two.

Arrange the atoms in the molecule so that the outermost energy level in each atom is full.

Another way of representing molecules is using
Couper notation . In this case, only the electrons that are involved in the bond between the atoms are shown. A line is used for each covalent bond. Using Couper notation, a molecule of water and a molecule of HCN would be represented as shown in figures
[link] and
[link] below.

A water molecule represented using Couper notationA molecule of HCN represented using Couper notation

Dative covalent bonds

A
dative covalent bond (also known as a coordinate covalent bond) is a description of covalent bonding between two atoms in which both electrons shared in the bond come from the same atom. This happens when a Lewis base (an electron donor) donates a pair of electrons to a Lewis acid (an electron acceptor). Lewis acids and bases will be discussed in
[link] in chapter
[link] .

One example of a molecule that contains a dative covalent bond is the ammonium ion (NH
4+ ) shown in the figure below. The hydrogen ion H
+ does not contain any electrons, and therefore the electrons that are in the bond that forms between this ion and the nitrogen atom, come only from the nitrogen.

Newton's second law of motion states that the acceleration of an object is equal to the net force exerted on the objectdivided by the object's mass. The direction of acceleration is the same as the direction of thenet force.

Sebastian

what is close vector diagram

Lebogang

can you describe the relationship between the netf exterted on an object and A of the object for me plz